Motion Control Instructions Motion Control Instructions eV+ processes robot motion instructions differently from the way you might expect. With eV+, a motion instruction such as MOVE part is interpreted to mean start moving the robot to location 'part'. As soon as the robot starts moving to the specified destination, the eV+ program continues without waiting for the robot motion to complete. The instruction sequence: MOVE part.1 SIGNAL 1 MOVE part.2 SIGNAL 2 causes external output signal #1 to be turned on immediately after the robot begins moving to part.1, rather than waiting for it to arrive at the location.
When the second MOVE instruction is encountered, eV+ waits until the motion to part.1 is completed. External output signal #2 is turned on just after the motion to part.2 begins. This is known as forward processing. See Breaking Continuous-Path Operation for details on how to defeat forward processing. This parallel operation of program execution and robot motion makes possible the procedural motions described later in this chapter. Basic Motion Operations Joint-Interpolated Motion vs. Straight-Line Motion The path a motion device takes when moving from one location to another can be either a joint-interpolated motion or a straight-line motion.
Joint-interpolated motions move each joint at a constant velocity (except during the acceleration/deceleration phases-see Robot Speed). Typically, the robot tool tip moves in a series of arcs that represents the least processing-intensive path the trajectory generator can formulate. Straight-line motions ensure that the robot tool tip traces a straight line, useful for cutting a straight line or laying a bead of sealant. The instruction: MOVE pick causes the robot to move to the location pick using joint-interpolated motion. The instruction: MOVES pick causes the robot to move the pick using a straight-line motion.
Safe Approaches and Departures In many cases you will want to approach a location from a distance offset along the tool Z axis or depart from a location along the tool Z axis before moving to the next location. For example, if you were inserting components into a crowded circuit board, you would want the eV+Language User's Guide, v2.x, 18318-000 Rev A Page 116